This invention relates to a light emission element array particularly used for a light source of an image sensor and also relates to a method of manufacturing the light emission element array of this character.
With an image scanner, a copying machine and other various inspecting apparatus, it is a matter of general knowledge that an image information is read out by inducing a light from a light source on a surface of a material such as an original or an object to be inspected and by carrying out a photoelectric conversion of a light reflected from the surface of the original, for example, by using a linear image sensor. Recently, a light emitting diode element (called hereinafter LED) has been widely used as the light source described above for the reason that the LED is excellent in the reliability and long life time. The LED of single element emits a small amount of light having a short light reaching distance, so that a LED array in which a plurality of LEDs are linearly arranged is generally utilized.
A known type of a LED array of this character comprises a row of LEDs and a columnar light converging lens unit arranged in parallel to the LED row to linearly converge the light on a predetermined position. However, the LED array having such structure or arrangement is liable to be varied in the light converging position because of certain reasons on the manufacture or usage thereof, and in particular, in case the LED array is utilized for an original read-out section of a copying machine, for example, the light converging position is liable not too often coincide with the original read-out position. This may cause a problem of unevenness of an output level from the read-out section even if the original with uniform reflection factor could be read because of unevenness of illumination at a portion of a read-out line or lowering of the entire illumination. Moreover, the processing of a signal having such uneven output level will require a complexed signal processing circuit, and even if the complexed signal processing circuit is used, an improved signal to noise ratio (S/N) has not been expected.